1. Field of The Invention
The present invention generally relates to a composite magnetic head for use in recording and/or reproducing information on a magnetic recording medium.
2. Description of the Prior Art
It is well known in the art that a loss of energy occurring in the magnetic head core as a result of generation of an eddy current when an electric current is supplied to a coil in the magnetic head brings about considerable reduction in high frequency characteristic, and this is particularly manifest where the magnetic head includes the head core made of an alloy having a low specific resistance.
By way of example, referring to FIG. 6 of the accompanying drawings, in the case of a thin plate made of an alloy having a specific resistance .rho., the loss We resulting from the eddy current per unit volume is expressed by the following equation. EQU We=.pi..sup.2 .multidot.h.sup.2 .multidot.f.sup.2 .multidot.Bm/6.rho.
wherein h represents the thickness of the thin plate, f represents the frequency of a recording signal to be recorded, and Bm represents the maximum magnetic flux density. This is attributable to the fact that at high frequency a skin effect occurs in the magnetic flux by reason of the eddy current, which skin effect brings about a substantial reduction in magnetic permeability .mu.. In other words, it is well known that the magnetic permeability .mu. of the alloy core abruptly decreases with an increase of the sound frequency f. As shown in FIG. 7 of the accompanying drawings, the magnetic permeability of the alloy core decreases to a value lower than the value of the ferrite core when the sound frequency attains a value higher than, for example, 10 KHz. (See, "Jiki-heddo to Jiki-kiroku (Magnetic Head and Magnetic Recording)" published Mar. 15, 1983 by Sogo Denshi Publishing Co.)
In view of the foregoing general notion, it is the well established practice to make the magnetic head using the alloy plate as thin as possible. An example of the prior art magnetic heads using the thin alloy plate is illustrated in FIG. 8 of the accompanying drawings. In the manufacture of the prior art magnetic head shown in FIG. 8, a main core 1, made of a thin alloy plate, and an auxiliary core 2, made of ferrite, are prepared independently and then joined together by a glass-bonding material which forms a glass layer 3 acting not only to bond the main alloy core 1 and the auxiliary ferrite core 2 together, but also to reinforce the main alloy core 1. The magnetic head shown therein has a groove 4 defined therein for the passage of transducer coil windings.
Another example of the prior art magnetic head is shown in FIG. 9 of the accompanying drawings, wherein the core 1 is made of Mn-Zn ferrite. However, the prior art magnetic head shown in FIG. 9 has a problem in that the saturation magnetic flux density is low.
In any event, the prior art alloy head shown and described with reference to FIG. 8 requires complicated manufacturing procedures with increased process steps as compared with the manufacture of the ferrite head shown in FIG. 9 wherein the core material has a high specific resistance, thereby posing a productivity problem. More specifically, in the manufacture of the prior art alloy head shown and described with reference to FIG. 8, the productivity is low not only because care is required to keep a relatively high flatness in the interface between the main alloy core 1 and the auxiliary ferrite core 2, to avoid any possibility of the main alloy core 1 being warped during the manufacture thereof, to avoid any possible reduction in bonding strength and to make the resultant alloy head with precision, but also because a number of minute chips are required to be carefully bonded during the manufacture of the alloy head.